B1026

#include<iostream>
using namespace std;
int main(){
int c1;
int c2;
int h,m;
double s;
cin>>c1>>c2;
h=(c2-c1)/360000;
m=(c2-c1-h*360000)/6000;
s=(c2-c1-h*360000-m*6000)/100.0;
int ss=(int)s;
if((int)(s*10)%10>=5)
ss++;
if(ss==60){
m++;
ss=0;
}
if(m==60){
h++;
m=0;
}
cout<<(h<10?"0":"")<<h<<(m<10?":0":":")<<m<<(ss<10?":0":":")<<ss;
}